Modern internal combustion engine designers employ a wide variety of metals in engine construction in order to obtain the best combination of light weight and performance. These metals may include aluminum and its alloys for water pumps and cylinder heads, brass for thermostats, copper/brass alloys or aluminum for radiators, cast iron for engine blocks or aluminum engine blocks with steel cylinder sleeves. When these diverse metals are combined in an internal combustion engine with a liquid cooling system, electrolysis is generated which erodes these different engine parts, causing early failure of many parts and necessitating expensive repairs.
Similarly, electrolysis and the corrosion which accompanies it is found in residential and industrial plumbing systems, again due to the many various metals which may be used for pipes, faucets, valve cartridges or the like. As in the cooling system of an internal combustion engine, these metals are electrically coupled by the liquid in the system, and electrolysis and corrosion may occur at any time.
In the past, especially in the marine industry, the most common method of dealing with undesired, destructive electrolysis was to install a sacrificial anode on the device (boat hull or outboard engine lower drive unit) to be protected from electrolysis. The sacrificial anode is formed from a metal, such as zinc, which will be attacked by electrolysis more readily than the material of the protected device, so that the anode is "sacrificed" to save the protected object. Usually, sacrificial anodes are easily replaced to facilitate their removal when used up and replacement with fresh elements for continued protection.